This project was part of the Colorado Department of Transportation’s ongoing reconstruction of I-225 from I-25 and I-70. The 2 mile reconstruction widened the existing highway to 3-lanes in each direction with an additional auxiliary lane. The project scope included removal of the existing pavement, earthwork, placement of median barrier, sound walls, MSE walls, soil nail walls, storm sewer and drainage improvements, electrical and signage upgrades, sub-grade improvements, and repaving with over 135,000 SY of 13” thick PCCP.
The Project design consisted of 13 inches of concrete pavement over a lime treated sub grade, providing for a long life, economical, cost effective pavement solution. This sustainable design choice provided for a reduced environmental footprint over the lifetime of the roadway by reducing the amount of construction resources, materials, energy, maintenance and rehabilitation over the roadway life cycle. During reconstruction, sustainable construction practices were as follows:
- The existing roadway was 100% recycled.All asphalt was hauled to a recycling center, while the existing concrete was crushed on site to produce coarse concrete aggregate and Class II backfill.The Class II backfill was re-incorporated into the project as structural fill for storm sewer and MSE walls.
- The original detour design changed from 12 inch asphalt to 7 inch concrete.This temporary pavement then would be recycled on site.This significantly reduced the demand on virgin materials and material trucking required for the project.
- The concrete mix design utilized on the project was optimized, developing a reduced cement content mix with fly ash replacement.This optimized mix design reduced the disposal needs of industrial byproducts, further reduced the demand on virgin materials and helped to conserve natural resources all while averaging over 700 psi flexural strength.
Approximately 30,000 tons of material was produced from the recycled concrete. This eliminated over 2,400 truck loads of material that did not have to be hauled from the site, or hauled in from a virgin source, significantly reducing the environmental impact. This equates to over 6.5 trips around the earth and a savings of over 25,000 gallons of fuel.
This project shows how concrete pavements can exhibit a lower energy footprint, reduce the use of fuel during construction, lower disposal needs and promote recyclable materials.